The invention relates to an electromagnetic flow meter, comprising a metering tube having a thick outer wall made of an electrically non-conducting material. It has at least two measuring electrodes and at least two magnetic poles, each of which is disposed in a blind bore of the metering tube. They are linked to one another by a yoke and have at least one magnetic coil.
In a known magnetic-inductive flow meter, as described for example in German patent publication DE-OS 15 73 066, the yoke linking the magnetic poles is disposed outside the periphery or outer surface of the metering tube. Such an arrangement requires an inordinate amount of space for the yoke and, for small diameters, results in significant losses of magnetic flux and a reduced sensitivity. These drawbacks are also encountered with arrangements in which the cores of the magnetic coils are mounted on a ferromagnetic housing for the magnetic reflux (cf. EP 0047342 B1; U.S. Pat. No. 4,089,113; German Patent DE 35 11 033).